This application claims the priority benefit of Taiwan application serial no. 89122539, filed Oct. 26, 2000.
1. Field of the Invention
The invention relates in general to planarization method. More particularly, this invention relates to method of chemical mechanical polishing (CMP) an organic silicon material with a low dielectric constant.
2. Description of the Related Art
As the line width of semiconductor keeps shrinking, a mass production of ultra-large integrated circuit with high speed, multi-functions, high integration, low power consumption and low cost can be achieved. Due to the increasing integration, the density of interconnects is increased to cause a longer the resistance-capacitance delay (RC delay) to reduce the device speed. Therefore, materials with low dielectric constant have been used as the insulation layers between the interconnects to decrease the stray capacitance between conductive lines, and to result in a higher operation speed of the device.
Currently, the commonly used material with a low dielectric constant includes polymer chemical compound such as the organic silicon compound having the Sixe2x80x94Rn bond (R is the functional group, n equal to 1 or 2), for example, the polysiloxane compound is an example. This kind of material can be formed on a substrate via spin coating followed by baking and curing. The material of methylsilsequioxane (MSQ) with a dielectric constant of about 2.6 to 2.8 with Si-Ch3 bond is frequently used in the advanced semiconductor fabrication process. On the other hand, due to the reduction in size for devices, the exposure depth is inevitably reduced, so that the planarization step becomes a crucial step for fabricating multilevel interconnection. Among the current available planarization processes, chemical mechanical polishing is one the best methods to achieve a global planarization. Therefore, the chemical mechanical polishing performed on the organic silicon material with a low dielectric constant becomes critical in the later part of the fabrication process.
The organic silicon material with a low dielectric layer is a high carbon content polymer. While polishing such material with the slurry for polishing silicon oxide thin film, the polishing rate is significantly reduced due to the high carbon content. Moreover, scratches and non-uniformity on the polished surface are very likely to occur. Therefore, a new slurry has to be developed to provide a better polishing results. However, many experiments and analysis are still required to find out the appropriate slurry that would increase the polishing rate without damaging the polished surface.
The invention provides a method of chemical mechanical polishing an organic silicon material with a low dielectric constant. An organic silicon material with a low dielectric constant is formed on a substrate. An oxygen plasma treatment is performed on the organic silicon material to remove carbon content from the organic silicon material. A chemical mechanical polishing process is performed on the organic silicon material after the oxygen plasma treatment. An ammonia plasma treatment is further performed to mend the damages of the organic silicon material.
By the above method provided by the invention, the carbon content is removed prior to performing the chemical mechanical polishing process. Therefore, the polishing rate is enhanced. By performing the ammonia plasma treatment, the damages caused by the oxygen treatment, or even by chemical mechanical polishing can be mended to reduce low leakage current of the polished surface.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.